1. Field of the Invention
The present invention relates generally to audible signalling systems which utilize a piezoelectric component to provide an audible signal and which include circuitry for sufficiently driving the piezoelectric component to produce the audible signal. More particularly, the present invention relates to circuit means electrically coupled to the circuitry for driving the piezoelectric component for producing a sharp attack audible sound followed by a decay in sound level which is a characteristic of a chime tone audible signal.
Generally speaking, the audio system of the present invention includes an audible signalling circuit which includes a piezoelectric transducer, circuitry for driving the audible signalling circuit whereby a pulsed audible signal is provided by the piezoelectric transducer, and circuit means electrically interposed between the audible signalling circuit and the circuitry for driving the signalling circuit for exponentially decaying the pulsed audible signal whereby a chime tone audible signal is produced.
2. Description of the Prior Art
One of the major problems associated with previous audible signalling systems and/or devices is their inherently unpleasant sound. For example, in automobile alarm systems or audio indicators and in paging systems the audible signal produced is typically constant and at a peak sound level until discontinued. While in some applications an audible signal which continuously produces a peak sound level is desirable, it is many times desirable or required that the audio output be less irritating and more pleasing to the listener. A common less irritating audible signal is a chime tone audible signal where a periodic instantaneous peak sound level is produced which gradually dissipates over a period of time before a subsequent peak sound level is again produced.
Various audible signalling systems exist in the prior art for producing a chime tone audible signal most of which require complex circuitry to operate and/or are too large to be utilized in many applications such as the previously discussed automobile audio indicators and paging systems. Furthermore, many audible signalling systems can exhibit a nonlinear relationship between audio output and electrical input and also exhibit a large frequency change over a range of electrical inputs. By utilizing a piezoelectric transducer and appropriate associated circuitry, a chime tone audible signal may be produced which alleviates the problems enumerated hereinabove.